Think of it this way, One Piece World is created or modified using Haki, it's like a Matrix or Dream World where the Ink is Haki
(Oda basically Hinted at this in SBS when He talked about Energy responsible for everything in Universe)
Rayleigh said every Living Being has Haki inside them, what is it's Purpose?
It is what allows all of them to Live in this World & Interact with it
(Similar to Vegapunk's Light Gloves, They allow them to interact with Holograms, it's just that with OPVerse People, They have it Naturally)
This is also even though "Souls" exist in One Piece World & They are indeed Source of Life, Haki can also Kill a Person
As Luffy & later Zoro also confirmed that if you Spend your entire Haki, You will Die, so this Haki Energy is indeed related to Ability to Live in this World
It's also why Haoshoku Haki Victims lose their Senses & Pass Out, it's cuz They encounter an Overwhelming Charge of Haki, that They are unable to withstand, it's like They get Disconnected from The World (Like a GPU unable to run a Game)
Originally, those who Learned how to Harness their Haki Energy, were able to Use it in Three Ways, CoO, CoA & CoC (Actually the Fact They are called "Colors" is another Hint that this entire World is Fake & Haki is shaping it, just like Miss Goldenweek Colors can modify both Emotions & Appearances)
CoO pushes your Awarness even further allowing to not just sense the World as Normal People do, but also Haki itself, hence why They are able to Detect Power Levels, Presence, some Intentions ... etc. Then We have CoA which allows you to cover yourself or what you touch in Haki, which if you ignore DFs (Who didn't always exist) is pretty much Useless cuz what would this Ability unable you to touch before DFs existed?
It's none other than Haki Beings. And finally CoC allows you to rule over Haki, in other words such Beings
So Overall, i believe there exists a Race of Beings made of Pure Haki, and based on what i just explained, They are naturally considered "World Creators" cuz They are made of what Shapes/Controls it, They were seen as Gods by some & feared by others (And We did see them in Skypiea, when Conis showed them how They shaped Vearth that They worship, it was in a Form of a Devilish Being)
I can give you Dozens of Hints from every Single Arc about these Devils & how Oda is preparing for their Major Introduction, but let's just say that Imu & Gorosei Transformation wasn't from Zoan Fruits, it was their True Devilish Forms cuz They are Celestial Dragons (Also called Creators & Gods) and that's why Sabo (A Logia) was Extremely Hurt by Imu's Attack, Imu wasn't applying Haki on his Attack, it was a Tail made of Pure Haki
As for Devil Fruits? They have those Swirling Patterns which are the same as Vinsmoke Family Eyebrows which Oda explained is same as Circular Energy that runs the Universe, so Devil Fruits are like Mini-Worlds in themselves, like Mini-Dreams (Which Vegapunk basically confirmed) and They are created using a Devil (Sentient Haki) + People's Dreams (Which are taken by Imu from People's Wealth AKA Heavenly Tribute & those 16 Bullets References are based on Theory of 16 Desires, meaning CDs steal People's Desires/Dreams for their own Twisted Plans)
So when someone eats a DF, They are basically gaining the ability to shape the World just like that Devil inside them and it's only limited to one power, it's like They have a Mini-Dream inside them which They can apply on Reality, and They can't eat a Second DF, cuz u can't have Two Dreams (Simultaneously), or as Jabra hinted at (Two Devils will Fight each other killing the Host)
And the reason They are weak in Water, is cuz it's their Source, The Devils inside DF Users gain power when submerged in Water which makes User unable to control their Body properly, which indicates that Devils & Haki belong in The Sea, it's like their Mother Source (Hence why We heard the word Sea Devil very often)
And think about it, if the Sea acquires all DF Powers, which is basically Ability to turn anything into Reality cuz you would be able to create Life (Zoans) + any Type of Land & Environment & Weather (Logia + Paramecia), so technically the Sea would be able to create Islands with infinite possibilities, so any Sailor can find any Island They dream of, it's like there is a Heaven for anyone (Any Dreamer)
But The Sea by itself can't do all this, it needs a Soul, a Willpower, someone who represents "Sea God" himself and controls it, in other words "The Dreamer" himself, the Person who would lead the World & create a Reality where everyone can share their Dreams, no need to take from others & hurt them so that you get what you want (Which is what every Villain Plot is about)
This Dreamer is none other than Blackbeard, meaning They are currently in Nightmarish Version of Story, and He never sleeps cuz how can anyone be asleep in their own Dream World? And Now Luffy is on Journey to change everything, or as Roger said once "Turn the World upside down" (One Piece means a Coin that has Two Sides)
I've talked too much, but i just wanted to elaborate more about why i believe One Piece Story is much more complicated than people realize
